I have an inline refugium setup a little bit different from you drawings. DT drains to sump (first section has skimmer), and the second section (also last) of the sump is divided in half, one for return and one for another pump that runs a manifold to feed the 30 gal refugium (along with other stuff). The refugium then drains back into the actual return section. Technically, just one pump could be used for return and the manifold, but I have used 2. I did quite a bit of research when trying to figure out how to do this, and this made the most sense for myself.
Basically, it's pretty close to Titans_Reef setup from the sound of it... my pump for the fuge is in a slightly different spot.